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Abstract
Children from low socioeconomic (SES) families are exposed fewer words compared to children from middle-income families, and as a consequence, often score lower on standardized vocabulary assessments (Hart & Risley, 1995) such as the Expressive Vocabulary Test (EVT). Words that are acquired as part of ones vocabulary are influenced by cultural experiences. An alternative measure, D, has been proposed to assess lexical diversity by comparing the number of unique words with the total number of words in a language or writing sample (Malvern, Richards, Chipere, & Durn, 2004). D provides an alternative measure to vocabulary deployment that is not linked to a childs knowledge of specific vocabulary words. The primary purpose of the current study is to validate D as a useful measure for lexical diversity in at-risk, low-income, predominantly African American children. D was validated using Kanes argument-based approach to validity (1992). Five assumptions were proposed to validate D as a measure of lexical diversity and are grounded in research regarding the validation of standardized vocabulary assessments in multicultural populations.Based on the five assumptions, the findings from this study provide some evidence in support of D as a valid measure for evaluating lexical diversity in low-income children who are predominantly African American. D was found to be somewhat related to expressive vocabulary; the relationship was weak and therefore suggests that D measures an aspect of vocabulary that is related to but different than expressive vocabulary. Further, there were no differences in D between African American and non-African American children. This suggests that D may overcome the racial-bias exhibited in standardized assessments. Previous research in standardized vocabulary tests found that these measures can be racially-biased with low-income children performing lower than the standardized mean and African American children performing even lower within that group. The evidence collected in this study provides support that D is generalizable across races and SES, and could be a useful supplement to standardized measures of vocabulary. The use of standardized and nonstandardized measures together could more effectively screen and detect early language deficits in order to determine language ability and guide intervention efforts.